In certain instances it is desireable to achieve rapid printing of computer-generated information which can not be satisfactorily handled by conventional high speed computer peripheral printers. Some applications, for example, may require special purpose indicia which are not available on conventional high speed printers, or can not be provided on such printers without unacceptable size reductions. In addition, the special purpose indicia may have certain security problems associated therewith, if the indicia have value validating significance. One application in which one or both of these problems may arise is the preparation of paychecks; and another is the printing of postage.
With regard to the postage printing application in particular, it is conventional for high volume mailers to avail themselves of the high speeds offered by modern electronic digital computers and output printers, in order to increase their output. A typical prior art installation includes a computer which is programmed to receive information as to the weight and destination of a package, and from that information to calculate the required postage. A high speed chain printer is slaved to the computer to print out the destination information on an address label which is subsequently affixed to the package.
The computer also provides the calculated postage amount information to shipping department employees in some form which enables them to affix the proper amount of postage to the package. The most common way of accomplishing this is for the high speed printer to receive the postage amount information from the computer, and print it directly on the address label for the information of the employees. This print-out is not a government-authorized postage impression of the kind provided by a postage meter. The print impression made in a prior art installation as described above includes only the postage amount without any authorized postage validation symbols, and is provided for information only. Thereafter authorized postage of like amount must be affixed by an employee by means of postage stamps or a conventional manually controlled mechanical postage meter.
The intervention of a human being, or of a mechanical postage metering device, slows down a high volume mailing operation of the kind described. Therefore it is desirable to have the authorized postage impression printed automatically in response to the computer-generated postage calculation. Some form of secure, fixed-program postage accounting equipment must also be provided.
It would be possible to use a mechanical postage meter which comprises a secure housing containing authorized postage printing means, a mechanical descending register for storing the postal credit balance, and mechanical means for guaranteeing that all printed postage amounts are decremented from the register. An electrically actuated controller device may then be provided to translate electrical signals from the computer into mechanical inputs for controlling all meter functions.
The latter approach meets all security requirements, but is considered too slow to meet the speed requirements of some high volume mailing operations. When used in conjunction with an electronic digital computer and high speed printer, it may be necessary for the postage printer to produce approximately two or three postage impressions per second. Mechanical postage meters, however, typically are motor-driven printing devices with mechanical postage-amount-changing mechanisms. Their maximum output rate, about two postage impressions per second, is barely adequate for the application described. Moreover, their output rate drops to about half of that maximum if it is necessary to change the postage amount between print cycles. Thus the utility of mechanical meters in data processing environments is largely limited to fixed-postage-amount applications.
It is possible to use the printing capability of the high speed printer itself for postage purposes, by making appropriate modifications such as replacing standard print characters by special postage symbols. That approach, however, runs into the problem of character size limitations which are inherent in standard high speed printing equipment. It also involves undesirable interference with the electrical interface between the computer and the high speed printer, i.e., breaking into the electrical cable which connects the computer and the high speed printer in order to insert special circuitry for performing postage security accounting functions. It is also necessary to house the printer and the postal accounting circuitry in a large security enclosure to prevent cheating by an unscrupulous computer programmer.